Papers

Because of the nonideal directivity of loudspeakers in wave field synthesis, the conventional approach of individually equalizing each loudspeaker does not produce an accurate soundfield over an extended area of the listening space. A new method for equalization considers the full array of loudspeakers as a complete multiple-input multiple-output (MIMO) system. In the proposed multichannel inversion scheme, compensation is achieved for a limited ensemble of elementary virtual sources. Results show that the approach reduces rendering artifacts and spectral coloration over an extended listening area.

Equalizing a loudspeaker using a cascade sequence of second-order sections (low-pass, high-pass, or peak filter) is a viable alternative to the more conventional approach of a single large FIR filter. In order to optimize the parameters of each filter section, a two-step algorithm begins by first searching for a good initial solution and then applying a heuristic method using subjective criteria. The solution is scalable, subjectively validated, and produces a computational cost reduction in comparison to the conventional approach for the same degree of performance.

In contrast to the standard linear prediction-based perceptual audio coding that uses a separate psychoacoustic model, the authors propose Laguerre-based linear prediction employing a perceptually biased solution. This greatly reduces the computational complexity because a separate psychoacoustic model is no longer required. Subjective listening tests show that the resulting audio quality is similar to that of the traditional approach.

In recent years a number of speech quality prediction algorithms have been developed for evaluating telecommunications systems. The family of ITU-T recommendation P.862 is frequently used to create a mean opinion score of quality. Although these algorithms have been evaluated under common testing conditions for narrow- and wide-band speech signals, care must be used when these standards are applied to channels more specialized degradations, such as spectral aberrations, time scaling, and environmental noise. This study has discovered certain cases of suboptimal accuracy. As with the use of all quality-metric tools, the user must heed their limitations and scope of applicability in order to avoid erroneous conclusions.